(717a) Synthesis of Li-Doped MIL-53(Al) and Its Hydrogen Adsorption Property

The development of safe and efficient H₂ storage systems is required for the practical use of H2 as an alternative energy source to fossil fuels. The use of H2 adsorption on porous materials, especially on metal-organic frameworks (MOFs), is one of the most promising methods; however, the H₂ uptake of MOFs is limited due to their weak interactions with H₂. Recently, it has been shown that Li-doped MOFs can increase their H₂ uptake due to a strong interaction between Li and H₂.^1-3 However, peculiar organic ligands for Li ions should be introduced into the MOF skeleton. ^2,3 Therefore, a useful method of Li doping into MOFs should be established. Recently, we have succeeded in Li doping into mesoporous silica based on the release of the anion by the heat treatment after impregnation with an ethanol solution of LiCl.⁴ The Cl^- was released in the form of C₂H₅Cl as a result of reaction with ethoxy groups on silica. This method is extended to MOFs. In this research, the Li doping into MIL-53(Al), which is a highly thermally-stable MOF constructed from aluminum and terephthalic acid with 1D rhombic channels,⁵ was investigated impregnation with a LiNO₃ solution followed by the heat treatment in vacuum. During the heat treatment, the NO₃^- were released in the form of NOx, which were detected by in situ FT-IR, while the Li⁺ remained. The H₂ uptake at 77 K and atmosphere pressure increased from 1.63 wt% for the non-doped MIL-53(Al) to 1.76 wt% for the Li-doped MIL-53(Al). Further experimental details will be reported in the presentation.

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